What is the diffrence between DOL & RDOL starter (constructionally & by application)?
DOL [Direct On Line] starters are those that apply the full supply voltage to the motor when starting. RDOL [Reversible DOL] starters are simply two DOL starters in the same box and allow the motor to be started in one direction and then in the other direction. Assume that we are talking about three phase motors. Suppose a sheet-metal goods factory uses a 10 kW motor to drive a set of rollers. When sheet metal goods are being made, it is sometimes necessary to roll the sheet metal in one direction and then the other. DOL starting is the quickest way of getting a motor up to full speed but is amounts to imposing a short circuit on the supply for a few seconds. This is very disruptive and as a result, energy companies will not allow big motors to be started, DOL. The actual limit varies from place to place.